Lyme disease begins at the site of a tick bite, producing a primary infection with spread of the organism to secondary sites occurring early in the course of infection. Lyme disease is a progressive multi-system disorder and is the most common vector-borne disease in both North America and Europe. This disease was first described as a focus of pediatric arthritis patients in Old Lyme, CT (Steere, A. C., et al., Arth. Rheum., 20:17 (1977)). The association of this syndrome with the bite of the deer tick, Ixodes scapularis, led to the identification of the spirochete Borrelia burgdorferi as the causative agent (Burgdorfer, W., et al., Science, 216:1317–1319 (1982)). As culture isolation of the bacterium from clinical and field samples became more efficient, Baranton and colleagues described three pathogenic genospecies, B. burgdorferi sensu stricto (B. burgdorferi or B.b.s.s.), B. afzelii, and B. garinii (Baraton, G., et al., Int. J. Syst. Bacteriol., 42:378–383 (1992)). These are members of a species complex, B. burgdorferi sensu lato, which consists of at least 10 different genospecies (Piken, R. N., et al., J. Invest. Dermatol., 110:211–214 (1998); Postic, D., et al., Int. J. Syst. Bacteriol., 44:743–752 (1994); Valsangiacomo, C. T., et al., Int. J. Syst. Bacteriol., 47:1–10 (1997)). B. burgdorferi, B. afzelii and B. garinii are thought to be pathogenic and all are found in Europe, but in North America, B. burgdorferi is the only pathogenic genospecies found. Each of these three genospecies is associated with distinct clinical manifestations (Van Dam, A. P. et al., Clin. Infect. Dis., 17:708–717 (1993)). This implies that differences in genospecies may play an important role in the wide array of clinical manifestations observed in Lyme Disease.
As an infected tick begins to feed on a mammal, the synthesis of outer surface protein C (OspC) is induced (Schwan, T. G., et al., Proc. Natl. Acad. Sci. 2:2909–2913 (1995)). Thus, in early infection, OspC is the major outer membrane protein expressed by the spirochete (Fung, B. P., et al., Infect. Immun. 62:3213–3221 (1994); Padula, S. J., et al., J. Clin. Microbiol., 32:1733–1738 (1994)). Even through OspC has been demonstrated to have limited surface exposure (Cox, D. L., et al., Proc. Natl. Acad. Sci., 93:7973–7978 (1996); Mathiesen, M. M., et al., Infect Immun. 66:4073–4079 (1998)), OspC is a potent immunogen. Immunization with OspC is protective against tick-transmitted Borrelia infection (Gilmore Jr., R. D., Infect Immun. 64:2234–2239 (1999)). However, because OspC is highly variable in its sequence, the protection is limited to the Borrelia burgdorferi strain expressing the same immunizing OspC encoded by a specific allele. Challenge with heterologous isolates, expressing other ospC alleles results in infection (Probert, W. S., et al., J. Infect. D., 175:400–405 (1997)). OspC is very diverse (Jauris-Heipke, S., et al., Med. Microbiol. Immunol. 182:37–50 (1993)). Livey et al. found thirty-four alleles in seventy-six B. burgdorferi sensu lato isolates (Livey, I., et al., Mol. Microbiol. 18:257–269 (1995)).
Currently, Lyme Disease is treated with antibiotics. However, such treatment is not always successful in clearing the infection. Treatment is often delayed due to improper diagnosis with the deleterious effect that the infection proceeds to a chronic condition, where treatment with antibiotics is often not useful. One of the factors contributing to delayed treatment is the lack of effective diagnostic tools.
Furthermore, while antigens such as OspC are known to be protective, in some cases the existence of multiple alleles of these antigens greatly hinders the development of vaccines based on such antigens that would protect against more than one strain of Borrelia. Two independent trials of first generation vaccines for the prevention of Lyme disease, recently studied the efficacy and safety of a vaccine that is based on recombinant outer surface protein A (OspA) (Sigal, L. H. et al., N. Engl. J. Med 339:216–222, 1998; Steere, A. C. et al., N. Engl. J. Med. 339:209–215, (1998)). However, a vaccine that consists of recombinant OspA may require frequent booster immunizations. Natural infection with B. burgdorferi does not elicit an antibody response to OspA, as it does against OspC. What is needed is a selection of Borrelia antigens that can be used to either diagnose or vaccinate against all or most forms of Borrelia that cause systemic disease.
Differences in the frequency of B. burgdorferi, B. garinii, and B. afzelii in ticks and human infection has lead to the hypothesis that the different genospecies are differentially pathogenic (Picken, R. N. et al., J. Invest. Dermatol. 110:211–214, 1998; Van Dam, A. P. et al., Clin. Infect. Dis. 17:708–717, 1993). Nevertheless, the number of different strains within a given genospecies and the differences between the strains of a given genospecies as well as between genospecies impose obstacles in the development of immunogenic protein compounds for use as diagnostic and vaccine agents in the detection, prevention and treatment of Lyme disease. A number of investigators have used OspC as a serodiagnostic antigen for early Lyme disease (Fung, B. P. et al., Infect. Immun. 62:3213–3221, 1994; Gerber, M. A. et al., J. Infect. Dis. 171:724–727, 1995; Padula, S. J. et al., J. Clin. Microbiol. 32:1733–1738, (1994)). In these tests, the use of OspC as a diagnostic antigen gave highly specific, but not sensitive results. However, these studies included only one B. burgdorferi strain and therefore only one type of OspC. Routine tests for the diagnosis of Lyme disease also use a single strain protocol and therefore a single OspC allele for detection of antibody to the sprirochete. It is not clear what mixture of OspC proteins must be used to make useful diagnostic and vaccine tools, effective against more than one Lyme disease causing strains of Borrelia, if not against most if not all of the invasive strains within a genospecies. Preferably, such a mixture would be effective against all invasive strains of Lyme disease causing borrelia. 